Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$143.86	8.355%	$155.8795	$155.88	$155.90	$155.90
Purchase #2	$196.64	6.563%	$209.5455	$209.55	$209.55	$209.50
Purchase #3	$42.87	9.775%	$47.0605	$47.06	$47.05	$47.10
Purchase #4	$242.64	5.255%	$255.3907	$255.39	$255.40	$255.40
Purchase #5	$132.64	13.630%	$150.7188	$150.72	$150.70	$150.70
Purchase #6	$55.97	6.220%	$59.4513	$59.45	$59.45	$59.50
Purchase #7	$245.89	13.322%	$278.6475	$278.65	$278.65	$278.60
7 purchase totals =	$1,060.51		$1,156.6938	$1,156.70	$1,156.70	$1,156.70